Update chat_template.jinja

chat_template.jinja

@@ -1,10 +1,40 @@
 {{- bos_token -}}
+{#-
+  Fixed chat template for LiquidAI/LFM2.5-1.2B-Instruct.
+
+  Framework-agnostic — works with HuggingFace transformers apply_chat_template(),
+  vLLM, TGI, and any Jinja2-based rendering pipeline.
+
+  Bugs fixed in the upstream HF template:
+  1. content=None on assistant messages renders "null" (via tojson) instead of empty
+  2. tool_calls field on assistant messages is completely ignored — multi-turn tool
+     conversations lose all tool call context
+  3. content=None on tool messages renders "null" instead of empty
+
+  Tool call reconstruction: when assistant messages carry a tool_calls field (OpenAI
+  format), this template reconstructs them into LFM's native format:
+    <|tool_call_start|>[func_name(param="value")]<|tool_call_end|>
+
+  Handles function.arguments as either a Python dict (pre-parsed) or a JSON string
+  (OpenAI wire format). Dict arguments get full pythonic formatting; JSON strings
+  are embedded as-is (best effort — no from_json filter in standard Jinja2).
+
+  Options:
+    keep_past_thinking  (default: false)  — preserve <think> blocks in non-final assistant turns
+
+  Ref: https://docs.liquid.ai/lfm/key-concepts/tool-use
+  Ref: https://huggingface.co/LiquidAI/LFM2.5-1.2B-Instruct/blob/main/chat_template.jinja
+-#}
 {%- set keep_past_thinking = keep_past_thinking | default(false) -%}
+
+{#- Extract system prompt from first message if present -#}
 {%- set ns = namespace(system_prompt="") -%}
 {%- if messages[0]["role"] == "system" -%}
     {%- set ns.system_prompt = messages[0]["content"] -%}
     {%- set messages = messages[1:] -%}
 {%- endif -%}
+
+{#- Append tool definitions to system prompt -#}
 {%- if tools -%}
     {%- set ns.system_prompt = ns.system_prompt + ("\n" if ns.system_prompt else "") + "List of tools: [" -%}
     {%- for tool in tools -%}
@@ -18,28 +48,134 @@
     {%- endfor -%}
     {%- set ns.system_prompt = ns.system_prompt + "]" -%}
 {%- endif -%}
+
 {%- if ns.system_prompt -%}
     {{- "<|im_start|>system\n" + ns.system_prompt + "<|im_end|>\n" -}}
 {%- endif -%}
+
+{#- Find last assistant index for think-stripping logic -#}
 {%- set ns.last_assistant_index = -1 -%}
 {%- for message in messages -%}
     {%- if message["role"] == "assistant" -%}
         {%- set ns.last_assistant_index = loop.index0 -%}
     {%- endif -%}
 {%- endfor -%}
+
+{#- Macro: format a Python value in the style LFM was trained on -#}
+{#- Strings → double quotes (via tojson), bools → True/False, None → None -#}
+{%- macro pyval(v) -%}
+    {%- if v is none -%}None
+    {%- elif v is boolean and v -%}True
+    {%- elif v is boolean and not v -%}False
+    {%- elif v is string -%}{{ v | tojson }}
+    {%- elif v is mapping -%}{
+        {%- for mk, mv in v.items() -%}
+            {{ mk | tojson }}: {{ pyval(mv) }}
+            {%- if not loop.last -%}, {% endif -%}
+        {%- endfor -%}}
+    {%- elif v is iterable -%}[
+        {%- for item in v -%}
+            {{ pyval(item) }}
+            {%- if not loop.last -%}, {% endif -%}
+        {%- endfor -%}]
+    {%- else -%}{{ v }}
+    {%- endif -%}
+{%- endmacro -%}
+
+{#- Render each message -#}
 {%- for message in messages -%}
     {{- "<|im_start|>" + message["role"] + "\n" -}}
-    {%- set content = message["content"] -%}
-    {%- if content is not string -%}
-        {%- set content = content | tojson -%}
-    {%- endif -%}
-    {%- if message["role"] == "assistant" and not keep_past_thinking and loop.index0 != ns.last_assistant_index -%}
-        {%- if "</think>" in content -%}
-            {%- set content = content.split("</think>")[-1] | trim -%}
+
+    {%- if message["role"] == "assistant" -%}
+        {#- --- ASSISTANT MESSAGE --- -#}
+
+        {#- Get text content, treating None as empty -#}
+        {%- set text_content = message["content"] if "content" in message and message["content"] is string else "" -%}
+
+        {#- Reconstruct tool_calls into native format if present -#}
+        {%- set tc = message.get("tool_calls", none) if message.get is defined else message["tool_calls"] if "tool_calls" in message else none -%}
+        {%- if tc -%}
+            {%- set ns.tc_parts = [] -%}
+            {%- for call in tc -%}
+                {%- if call is mapping -%}
+                    {%- set func = call["function"] -%}
+                {%- else -%}
+                    {%- set func = call.function -%}
+                {%- endif -%}
+                {%- if func is mapping -%}
+                    {%- set fname = func["name"] -%}
+                    {%- set fargs = func.get("arguments", {}) if func.get is defined else func["arguments"] if "arguments" in func else {} -%}
+                {%- else -%}
+                    {%- set fname = func.name -%}
+                    {%- set fargs = func.arguments if func.arguments is defined else {} -%}
+                {%- endif -%}
+
+                {#- Arguments can be a dict (pre-parsed) or a JSON string (wire format) -#}
+                {%- if fargs is mapping -%}
+                    {#- Dict: format as pythonic key=value pairs -#}
+                    {%- set ns.kv_parts = [] -%}
+                    {%- for k, v in fargs.items() -%}
+                        {%- set ns.kv_parts = ns.kv_parts + [k + "=" + pyval(v)] -%}
+                    {%- endfor -%}
+                    {%- set ns.tc_parts = ns.tc_parts + [fname + "(" + ns.kv_parts | join(", ") + ")"] -%}
+                {%- elif fargs is string -%}
+                    {#- JSON string: embed as-is (no from_json in standard Jinja2) -#}
+                    {%- set ns.tc_parts = ns.tc_parts + [fname + "(" + fargs + ")"] -%}
+                {%- else -%}
+                    {%- set ns.tc_parts = ns.tc_parts + [fname + "()"] -%}
+                {%- endif -%}
+            {%- endfor -%}
+            {%- set tool_call_str = "<|tool_call_start|>[" + ns.tc_parts | join(", ") + "]<|tool_call_end|>" -%}
+        {%- else -%}
+            {%- set tool_call_str = "" -%}
+        {%- endif -%}
+
+        {#- Combine: text content BEFORE tool call markers -#}
+        {#- This ordering is safe for think-stripping: -#}
+        {#-   <think>...</think>text<|tool_call_start|>...<|tool_call_end|> -#}
+        {#-   split("</think>")[-1] → text + markers preserved -#}
+        {%- if text_content and tool_call_str -%}
+            {%- set content = text_content + tool_call_str -%}
+        {%- elif tool_call_str -%}
+            {%- set content = tool_call_str -%}
+        {%- else -%}
+            {%- set content = text_content -%}
+        {%- endif -%}
+
+        {#- Strip thinking from non-final assistant messages -#}
+        {%- if not keep_past_thinking and loop.index0 != ns.last_assistant_index -%}
+            {%- if "</think>" in content -%}
+                {%- set content = content.split("</think>")[-1] | trim -%}
+            {%- endif -%}
         {%- endif -%}
+
+        {{- content -}}
+
+    {%- elif message["role"] == "tool" -%}
+        {#- --- TOOL RESULT MESSAGE --- -#}
+        {#- Handle content=None gracefully (render empty instead of "null") -#}
+        {%- set content = message["content"] if "content" in message else "" -%}
+        {%- if content is none -%}
+            {%- set content = "" -%}
+        {%- endif -%}
+        {%- if content is not string -%}
+            {%- set content = content | tojson -%}
+        {%- endif -%}
+        {{- content -}}
+
+    {%- else -%}
+        {#- --- USER / SYSTEM / OTHER MESSAGES --- -#}
+        {%- set content = message["content"] -%}
+        {%- if content is not string -%}
+            {%- set content = content | tojson -%}
+        {%- endif -%}
+        {{- content -}}
+
     {%- endif -%}
-    {{- content + "<|im_end|>\n" -}}
+
+    {{- "<|im_end|>\n" -}}
 {%- endfor -%}
+
 {%- if add_generation_prompt -%}
     {{- "<|im_start|>assistant\n" -}}
-{%- endif -%}
+{%- endif -%}